ATMEGA32U4 ADC conversion

hello guys,

i need to use the ADC conversion of Atmega32u4 for some analog signals.

i read on the datasheet of Atmega32u4 that to do so the "AVCC" pin of 
the controller must be connected to the input supply voltage pin "VCC" 
through a LOW PASS filter.

my question is:

what kind of low pass filter should be appropriate for such task?

Thanks in advance